Arc-extinction casing for circuit-breaker



May 27, 1958 A. A. H. soUcHET 2,336,683

ARC-EXTINCTION CASING FOR CIRCUIT-BREAKER Filed Feb. 28, 1956 UnitedStates Patent ARC-EXTINCTION CASING FOR CmCUIT-BREAKER Andr A. H.Souchet, Nanterre, France, assignor to La Telemecanique Electrique(Societe Anonyme), Nanterre, France, a company of France ApplicationFebruary 28, 1956, Serial No. 568,311 Claims priority, applicationFrance August 29, 1955 1 Claim. (Cl. 20G-144) It is known that, incurrent-breaking devices and especially in those which have a protectivefunction and are intended to break currents of very high value(shortcir-cuits), it is necessary to provide devices for extinguishingthe are which is struck between the contacts which are in the process ofseparating.

This extinction is generally effected by blowing the arc, eithermagnetically or by compressed air, within the interior of a casing whichsurrounds the contacts. These casings are sometimesy formed by poleplates between which the blowing device lengthens the arc by incurvingit until it is extinguished.

In the arc-blowing casings of known construction, the arcs which areproduced at the moment of the breaks give rise to llames which passoutside the casing and are liable to reach the metallic parts located inthe vicinity. In this way there may be produced destructive arcs whichare liable to produce, by short-circuit, melting of the conductivemembers of the apparatus.

It thus becomes essential to leave large air spaces, known as safetyperimeters between the casings of the circuit-breaker apparatus and themetallic casings in which they are housed. In the same way, in order toprevent arcing between adjacent poles, it is necessary to locate thepoles at fairly large distances from each other.

The present invention has for its object a blowing casing in which therupture of the electric current is obtained with practically no externalsign of its occurrence. In a casing of this kind, the flames of the arcare prevented from passing out of the casing; the casing however enablesthe gases heated by the flames to be evacuated.

In accordance with the invention, the casing is formed by a portion inthe shape of a convergent nozzle which encloses the contacts, thisnozzle opening through a narrow passages into an expansion chamber whichcommunicates with the exterior. Preferably, and in known manner, theportion in the form of a nozzle is divided into compartments by means offins orientated in the general direction of the nozzle, these tinstending to split up the arcs and cool the gases produced by the arcs.

In an advantageous form of construction, the nozzle and the expansionchamber have a common wall and the communicating passage between thesetwo spaces is delimited between the edge of this common wall and apartition which is substantially at right angles to the said wall, andwhich forms at the same time the space of the nozzle and that of theexpansion chamber.

This arrangement has a two-fold advantage; on the one hand the choice ofthe position of the partition with respect to the common wall enablesthe dimensions of the narrow passage to be regulated, and on the otherhand, the gases passing out of the nozzle are slowed down by theircontact with the partition and they pass into the expansion chamber in adirection which is practically opposite to that of their passage out ofthe nozzle.

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This passage in the form of a baffle assists the effect of cooling andof slowing down of the gases.

The casing is preferably formed by two pole plates having the generalshape of quarters of a circle, coupled at their periphery by apartition, the pole plates being hollowed out, on the one handinternally so as to form a flattened nozzle when they are broughttogether and on the other hand, in the thickness of these poleplates,`on each side of the said flattened nozzle, so as to form theexpansion chambers.

The description which follows below with regard to the attached drawings(which are given by way of example only and not in any sense by way oflimitation) will make it quite clear how the invention may be carriedinto effect, the special features which are brought out, either in thedrawings or in the text, being understood to form a part of the saidinvention:

Fig. l shows in cross-section, following the line I--I of Fig. 2, anarc-extinction casing improved in accordance with the invention. Y

Fig. 2 is a cross-section taken along the line II-II of Fig. l.

Fig. 3 shows a cross-section, similar to that of Fig. 2, of analternative form of embodiment.

In the device shown in these figures, the current reaches the incurvedxed contact 1 through a metallic winding 2 which is intended to create amagnetic field which ensures the extinction of the arc. This eld isguided along a core 14 of magnetic metal, which assembles together themagnetic pole plates 12 held in place by the. insulating cross-member I3in the form of a reel. In the case of high nominal current values, thiswinding may be reduced simply to a bar which passes through and which issufficient to create the necessary magnetic field.

With the contact 1 co-operates the moving contact 3 which can pass fromthe position shown in full lines (closed position) to the open position3a shown in dotted lines. When the contacts are opened, the arc which isstruck between the contacts 1 and 3 moves along these contacts towardsthe exterior and extends in a curve under the effect of the magneticfield. This arc is thus developed between the insulating jaws 4, whichhave the general shape of a quarter of a circle, of the arc casing.These jaws are hollowed-out internally so as to form a kind ofconvergent attened nozzle 5 which is directed towards the periphery ofthe casing. In the narrower portion of the nozzle are arranged the finsor blades 6, the general direction of which is radial. These tins may befitted into slots formed in the pole plates. The pole plates areconnected together by an incurved partition 7 of insulating material,which is fitted into oppositelydisposed slots in the pole plates, andwhich practically closes the casing, with the exception of the smallspaces 8 formed between the partition 7 and the edge 9 of theperipheries of the pole plates which constitute the extremity of thenozzle 5.

In the jaws 4 are formed hollow spaces 10 which, with the partition 7,form expansion chambers which communicate with the nozzle through thespaces 8. Towards the top of the casing, there is a gap in the partition7, so that the spaces 10 of the jaws communicate with the exteriorthrough the openings 11.

The device which has just been described operates in the followingmanner:

The gases heated inside the casing by the arc, as it curves outwards,are increased in speed by the convergent nozzle 5 and are thus led intothe narrow part of this nozzle. When the arc comes into contact with thefins 6, it becomes split up by these fins and the small sections of arcare extinguished in each of the compartments which are formed by thelins. In effect, by reason of the presence of the partition 7, there isproduced a pressure of gas towards the extremity of the paths followedby the arc elements, and this pressure assists the rupturing power sincethe dielectric rigidity of ther air increases with pressure. Thehotgasespass through the narrow spaces@ which draw Ythem out and give-them a curved trajectory, so that the gases'are very powerfully cooledduring this passage. The gases then expand into the chambers 10 andvthisstill further accentuates the cooling effect. From the chambers '10, thegases, escape to the exterior, either 'through 'the open-r ings 11 whichcan be directed in such manner that the gases cannot in any event bedangerous, or through the base of the casing where the chambers `10 maynot be entirely closed.

.,'The dimensions of the spaces 8 canv be fixed by experiment inaccordance with the values of current to be broken. In fact, if thesespaces 3 are too great, the effect of gas pressure which contributes tothe extinction kof the arcs is not obtained, and ames may pass outthrough the openings of the chambers 1t), whilst if these spaces are toosmall, the gas pressure obtained at the extremities of the nozzle maybeexcessive so that 'the arcs are forcedback, and this may give rise to.the production of fresh arcs on the contacts which are in course ofseparation, resulting lin 'damage to the contact surfaces.

In order to simplify the construction, as shown in Fig. 3, the partition7 may have a U-section which encloses the section of the casing. ln thiscase, the hollow spaces 10 are formed on the external faces of thecheeks.

It will of course be understood that modifications may bemade to theforms of embodiment which havebeen described above, in particular by thesubstitution of equivalent technical means Without thereby departing'from the spirit or from the scope of the present invention.

What I claim is: f

In combination with a circuit-breaker having sep- 4 l arable contactmembers liable to give rise to an arc upon separation thereof, anarc-extinction device comprising a attened chamber in which said contactmembers are housed, a at convergent nozzle communicating with saidchamber and forming an extension thereof, and a wall extending oppositethe discharge end of said nozzle at a distance therefrom to provide alateral restricted passage between said wall and said nozzle end,whereby any hot gases generated in said chamber upon formation thereinof an arc, expand through said nozzle and issue therefrom in the form ofa jet striking said wall and diverted thereby into said lateralrestricted passage, said flattened chamber being in the general shape ofa sector of a circle, said flat nozzle extending along theperiphery ofsaid sector over a generally circular arc, and said wall extending overan arc of a circle substantially concentric with the former-mentionedarc, said device further comprising two elongated and flattenedexpansion chambers extending on both sides yof the nozzle andcommunicating therewith, and said expansion chambers extending over arcsof a circle and having, lat one end thereof, an outlet aperture openingto the atmosphere.

References Cited in the iile of this patent UNITED STATES PATENTS1,836,994 ASlepian Dec. 15, 1931 2,215,797 Sauer Sept. 24, 19402,292,158 Prince Aug.14, 1942 2,293,452 Boehne Aug. 18, 1942 2,393,164Hobson Jan. l5, 1946 v2,555,993 Oppel et al. June 5, 1951 v2,633,518Miller Mar. 31, 1953 FOREIGN PATENTS '732,196 'Great Britain June 22,1955

